Chronic toxicity of tributyltin to Chesapeake bay biota

Chronic tributyltin toxicity experiments were conducted with the following Chesapeake Bay organisms: amphipod, Gammarus sp.; juvenile Atlantic menhaden, Brevoortia tyrannus and larval inland silverside, Menidia beryllina. TBT concentrations ranging from 29 to 579 ng L^?1 did not significantly affect survival of the benthic amphipod, Gammarus sp. after 24-d exposures. The weight of Gammarus exposed to control conditions was 2.8 times greater than the weight of these test organisms exposed to 579 ng L^?1 TBT. Twenty-eight day exposures to TBT concentrations of 93 and 490 ng L^?1 did not significantly affect survival of juvenile B. tyrannus or larval M. beryllina. Histological examinations of B. tyrannus did not demonstrate absolute effects resulting from TBT exposure due to extensive variation between individuals. Various morphometric measurements of M. beryllina after TBT exposure did not demonstrate significant effects. However, significant reductions in growth were reported for M. beryllina at both TBT concentrations. Environmental concentrations of TBT in Chesapeake Bay and possible effects on the above biota are discussed.     

New method for the determination of 1,1-dimethylhydrazine residues in apples and peaches

A new method for determining 1,1-dimethylhydrazine (UDMH) in peaches and apples is presented. The method consists of extraction with L-ascorbic acid, derivatization with 2-nitrobenzaldehyde to the corresponding hydrazone, and cleanup on an alumina column. The hydrazone derivative is determined by gas chromatography using an electron-capture detector. Recoveries were determined from 10 to 100 ppb. Stability of the UDMH residues on frozen peaches was investigated, and results indicate that the residues degrade even while frozen.     

Long-term tillage and cropping effects on microbiological properties associated with aggregation in a semi-arid soil

Little is known about the long-term tillage and cropping management effects on the microbiologically derived factors that influence macroaggregates in semi-arid soil. We tested the hypothesis that differences in macro-aggregation are due to changes in soil structure related to management treatment-induced microbiological changes. In an experiment, microbiological factors consisting of aggregate stability, glomalin, russuloid basidiomycete fungi, uronic acids, total organic C (TOC), and total N (TN) were quantified in macroaggregate-size classes ranging from 4.75 to 0.25 mm, collected at 0–5 cm depth for the following treatments: (1) 12th year of fallow phase after 11 years of conventional- and no-tilled spring wheat-fallow (CTF and NTF), (2) 12th year of lentil phase after 11 years of conventional- and no-tilled spring wheat-lentil (CTL and NTL), (3) 12 years no-tilled continuous spring wheat (NTCW), and (4) 16 years uncultivated pasture (P) used as a baseline treatment. Immunoreactive easily extractable glomalin concentration was five to six times greater under P, NTCW, or NTL in the 2.00–1.00- and 1.00–0.50-mm macroaggregate-size classes than the other treatments and these results corroborated well with the results from aggregate stability assays. Russuloid basidiomycetes were highest in all NTCW macroaggregate-size classes, suggesting that annual input of lignin-containing wheat residues may influence the growth and survival of these fungi. Uronic acid amounts were highest in P but did not differ among the other treatments. In all macroaggregate-size classes, TOC content was greater in NTCW compared to CTF, and TN was about three times higher in NTL than NTF or CTF. In conclusion, 12 years of NTCW management in semi-arid soil has resulted in higher macroaggregate stability, glomalin concentration, russuloid basidiomycete populations, and TOC in macroaggregates compared to alternate-year fallow. Lentil can be used to replace fallow in dryland wheat rotation under no-till to enhance TN content and improve soil macro-aggregation.     

Long-term tillage effects on the distribution patterns of microbial biomass and activities within soil aggregates

The effects of tillage on the interaction between soil structure and microbial biomass vary spatially and temporally for different soil types and cropping systems. We assessed the relationship between soil structure induced by tillage and soil microbial activity at the level of soil aggregates. To this aim, organic C (OC), microbial biomass C (MBC) and soil respiration were measured in water-stable aggregates (WSA) of different sizes from a subtropical rice soil under two tillage systems: conventional tillage (CT) and a combination of ridge with no-tillage (RNT). Soil (0–20 cm) was fractionated into six different aggregate sizes (> 4.76, 4.76–2.0, 2.0–1.0, 1.0–0.25, 0.25–0.053, and < 0.053 mm in diameter). Soil OC, MBC, respiration rate, and metabolic quotient were heterogeneously distributed among soil aggregates while the patterns of aggregate-size distribution were similar among properties, regardless of tillage system. The content of OC within WSA followed the sequence: medium-aggregates (1.0–0.25 mm and 1.0–2.0 mm) > macro-aggregates (4.76–2.0 mm) > micro-aggregates (0.25–0.053 mm) > large aggregates (> 4.76 mm) > silt + clay fractions (< 0.053 mm). The highest levels of MBC were associated with the 1.0–2.0 mm aggregate size class. Significant differences in respiration rates were also observed among different sizes of WSA, and the highest respiration rate was associated with 1.0–2.0 mm aggregates. The C_mic/C_org was greatest for the large-macroaggregates regardless of tillage regimes. This ratio decreased with aggregate size to 1.0–0.25 mm. Soil metabolic quotient (qCO₂) ranged from 3.6 to 17.7 mg CO₂ g^− 1 MBC h^− 1. The distribution pattern of soil microbial biomass and activity was governed by aggregate size, whereas the tillage effect was not significant at the aggregate scale. Tillage regimes that contribute to greater aggregation, such as RNT, also improved soil microbial activity. Soil OC, MBC and respiration rate were at their highest levels for 1.0–2.0 mm aggregates, suggesting a higher biological activity at this aggregate size for the present ecosystem.     

Increased cartilage oligomeric matrix protein concentrations in equine digital flexor tendon sheath synovial fluid predicts intrathecal tendon damage

Objectives: To evaluate digital flexor tendon sheath (DFTS) synovial fluid cartilage oligomeric matrix protein (COMP) concentrations as a molecular marker for intrathecal pathology. Study Design: Case control study. Animals: Horses (n=46) with DFTS tenosynovitis; 23 fresh cadaver horses. Methods: DFTS synovial fluid samples were collected from clinical cases with noninfected DFTS tenosynovitis and from control DFTS. Clinical and surgical findings were recorded, and dissection of control limbs was performed to confirm the DFTS to be grossly normal. Synovial fluid COMP was quantified using a homologous competitive inhibition ELISA. Results: Abnormalities were identified tenoscopically: intrathecal tendon/ligament tearing was identified in 37 cases and 9 had other lesions. In control horses, synovial fluid COMP was higher in younger horses. Clinical cases with intrathecal tendon/ligament tearing had higher synovial fluid COMP than either clinical cases with other lesions, or controls. In horses ≥5 years old, the sensitivity and specificity of the assay was high for diagnosing intrathecal tendon/ligament tearing. Conclusions: COMP concentrations in DFTS synovial fluid were significantly greater than those in normal horses with noninfected tenosynovitis caused by intrathecal tendon/ligament tearing, but not by other lesions.     

Salmonella Cerro isolated over the past twenty years from various sources in the US represent a single predominant pulsed-field gel electrophoresis type

Salmonella Cerro prevalence in US dairy cattle has increased significantly during the past decade. Comparison of 237 Salmonella isolates collected from various human and animal sources between 1986 and 2009 using pulsed-field gel electrophoresis, antimicrobial resistance typing, and spvA screening, showed very limited genetic diversity, indicating clonality of this serotype. Improved subtyping methods are clearly needed to analyze the potential emergence of this serotype. Our results thus emphasize the critical importance of population-based pathogen surveillance for the detection and characterization of potentially emerging pathogens, and caution to critically evaluate the adequacy of diagnostic tests for a given study population and diagnostic application.     

Genetic variability of Chlamydophila abortus strains assessed by PCR-RFLP analysis of polymorphic membrane protein-encoding genes

Torque teno viruses (TTVs) are vertebrate infecting, small viruses with circular single stranded DNA, classified in the Anelloviridae family. In pigs, two different TTV species have been described so far, Torque teno sus virus 1 (TTSuV1) and 2 (TTSuV2). TTSuVs have lately been linked to postweaning multisystemic wasting syndrome (PMWS). In the present study, TTSuV1 and TTSuV2 prevalence and DNA loads in longitudinally collected serum samples of healthy and PMWS affected pigs from Spanish conventional, multi-site farms were analyzed. Serum samples were taken at 1, 3, 7, 11 and around 15 weeks of age (age of PMWS outbreak) and viral DNA loads determined by quantitative PCR. For both TTSuV species, percentage of viremic pigs increased progressively over time, with the highest prevalence in animals of about 15 weeks of age. TTSuV1 and TTSuV2 viral DNA loads in healthy and TTSuV1 loads in PMWS affected animals increased until 11 weeks of age declining afterwards. On the contrary, TTSuV2 DNA loads in PMWS affected pigs increased throughout the sampling period. It seems that TTSuV species differ in the in vivo infection dynamics in PMWS affected animals.     

Growth and yield of soybeans under wet soil culture and conventional furrow irrigation in south-eastern Australia

Summary An experiment was conducted to determine the growth and yield responses of two soybean cultivars (Ridley and Sab40) grown on raised beds with continuous water applied in furrows (wet soil culture, WSC), and with conventional furrow irrigation applied at soil water deficits of 35 mm (F) and 70 mm (I). The early growth and leaf area development of both cultivars was reduced by both waterlogging (WSC) and water stress (1) effects compared to the frequently irrigated (F) treatment. Both cultivars acclimated to the WSC conditions and resumed active growth rates comparable to the F treatment. Excessive dry matter accumulation into leaves and stems of Ridley under WSC resulted in severe lodging and significantly reduced grain yield compared to Ridley under F irrigation. The physiological analysis presented showed that under WSC Ridley had a substantially lower light use efficiency compared the F irrigated crop during reproductive growth. It is hypothesised that lodging during this period reduced photosynthate supply as a result of detrimental changes in the pattern of leaf illumination throughout the canopy. The cultivar Sab40 did not lodge under WSC and grain yield was not significantly different from the F irrigated treatment.Further studies on the response of lodging resistant cultivars and different sowing time by plant arrangements to WSC are required to fully assess this technique under commercial conditions. More importantly, studies on soybean production in relation to crop water use and deep drainage losses on a range of soil types are needed to demonstrate that irrigation water applied is used as efficiently as conventional methods.